Метаболизм хичээлийн удиртгал: Анаболизм ба катаболизм

Метаболизм ба энерги

Video transcript

- [Voiceover] What I want
to do in this video is talk about the processes that
make all life as we know it, life as we know it, and at it's essence, we
can call this metabolism. Metabolism. And this is the taking
energy in different forms, breaking it down into its
more fundamental components, and then building it up in
ways that we would find useful, useful for energy, useful for structure, so that we can actually live our lives, we can grow, we can reproduce, we can respond to our surroundings. So as I just said, metabolism, and we're gonna go into a
bunch of examples of this. Metabolism at it's heart is
really two different processes. There's the breaking
down of the substances for energy or for
structure to getting back to the building blocks, and we call that catabolism. Catabolism. So this is the breaking down of things and then once we've broken down things, we're ready to rebuild them in ways that we would find useful, and we call this anabolism. Anabolism or anabolism. Anabolism, just like that. And one way to think about it is imagine that someone had
built something with Legos and you want to build
something with Legos. Well you could go to those Legos and you'd want to break it down, but not break it down too much. You wouldn't melt the plastic. You would break it down into
the individual Lego pieces and then you would build it back up into whatever shape that
you actually cared about. And you might not actually
have to even break it down all the way to the basic Lego pieces. There might be structures
in that first Lego castle that was constructed that
you might find useful. So let's just think about
how all of this gets started. And what's exciting is that
all of this got started, or gets started, from stars,
from fusion reactions in stars. And this right over here
is a picture of a star, and a star that we are very familiar with. This is the sun. But you may or may not
realize that the sun is only one of probably several stars that have been involved
in life as we know it. The sun is our most
direct source of energy for most of life as we know it. There are some bacteria and things that are able
to live off of vents at the bottom of the ocean
because of the heat created, but the sun is our
primary source of energy. But when I say that other
stars might have been involved, including dead stars that
existed billions of years ago, it's because the heavier
elements that we're composed of, or that are around us in the environment, the carbon, the oxygen,
we could just keep going, pretty much everything
other than hydrogen, it was constructed in fusion
reactions from hydrogen inside of stars. So we really are made up
of the remnants of stars. And so here we are, we're on Earth. Earth is all this condensed matter from four and a half billion years ago. Probably some nearby
supernova got all of this dust that was constructed in a previous star to coalesce in that way,
and you have radiation. You have energy from the sun. And once again, that energy's
coming from fusion reactions, and it's what fusing lighter
elements into heavier elements, so the sun is also constructing
more heavy elements, but that energy, that energy makes its way to the Earth. And you have organisms, like plants, that are
able to use that energy to construct the material, the food, we could say, that is eventually going
to get around to us. And so this process you may or
may not be familiar with it, this is photosynthesis. And we're going to go
into a lot more detail. Synthesis. And as the word implies,
photo, it's photosynthesis, it's making things out of light, and one thing I like to ask people when they are first
exposed to photosynthesis, is like okay, we can
see this grass growing or we can see this wheat growing, or we can see a tree growing, but where is that material coming from? And the most common answer is like, "Oh, somehow it's coming from the ground," and there are some nutrients
that are coming from the ground but it's really all about fixing carbon, and you're going to hear about this a lot especially as we talk
about the carbon cycle. But you have carbon dioxide
primarily in the air, so you have carbon, you have, I'll just write it this way. So you have carbon dioxide in the air and what photosynthesis
allows these plants to do is take the carbon in that carbon dioxide and form bonds with it, turn it from its gas
form into solid forms, into glucose molecules,
and then use that glucose to build up cellulose and to
build out other forms of starch and whatever else it might be. So it's taking these
molecules in the air... I'll just draw them as these little... It's taking these molecules that are in the air, and it's using the energy
of the sun to fix them, to actually form bonds between the carbons and with other things. As we said, we're mostly
carbon and hydrogen and we have some oxygen in there, but we're able to form these structures. Now from there other living organisms, and this is a huge oversimplification, it could involve bacteria, it could involve all sorts of things. And just a reminder, you
know, that photosynthesis, it isn't just light and it
isn't just the carbon dioxide. It also involves the water
and we talk about that. So you also have water involved. You also have the water involved. So you have the carbon dioxide, so CO2, light from the sun, and water. These things are able to grow
and nutrients from the Earth. And then from that, you're
able to construct things like, well, you can directly go to these plants that are taking energy from the sun and construct things like bread or you have other animals
that will eat things like the grass, and then break them down in their own way and they
will be assisted by bacteria and then rebuild themselves up into a cow, into milk. And so what this cow is doing, it's metabolizing this grass. It's able to break it down, it's able to catabolize the various molecules in the grass and break them
down into building blocks that can then used to build up the cow, to build up milk, and whatever else. And you might be saying, "What
are these types of molecules "that we keep breaking down "and then building back up?" Well, you have carbohydrates. Carbohydrates, and you're going to see
most of the molecules that I'm about to talk about. Frankly, all of them on the
back of nutritional package because it tells you what's inside of it. What is your body going to metabolize when it eats that whatever's inside of the package? So carbohydrates, these
are either simple sugars like glucose or fructose, or it could be polymers of these sugars, polysaccharides. It could be starches made up of many, many elements of the... Or many, many multiples
of these simple sugars. We could be talking about lipids. Lipids. So fatty acids, we could be
talking about cholesterols. These are essential structures, and they're also essential for, well, various metabolic pathways inside of, well, all of life, or it could be proteins. It could be proteins made up of amino acids. Sometimes people say the reason
why you want the proteins is because it's made up
of these amino acids. So you could break down these proteins and get the amino acids
and then build it up into new proteins. Proteins and amino acids. And all of these things, they are found in things like in the foods, in the foods we eat, which we will then consume, we will then metabolize. We will first catabolize
them and break them down and then we will use those building blocks to build it back up. And at the end of the day,
these provide the structures that make our bodies what they are. They allows us to interact
with our environment and they provide energy, and that energy, at the end of the day, the true molecular
currency for that energy is a molecule called ATP. That's a molecule of ATP right over there. Adenosine triphosphate. And the key for ATP, why it
is the molecular currency for energy, are the
three phosphate groups. So it has these three phosphate groups and we have a whole video on it, or a whole series of videos on it really, but the main key is that there's a lot of energy, especially beween I guess
on the last phosphate group. And this energy and that bond as the phosphate group
breaks off it can release it to provide all sorts of life mechanisms including being able to metabolize things. So ATP right over here,
this is the currency of energy in life as we know it. And it's actually an interesting molecule because it's essentially,
it's a piece of... If you were to just take this
section of it right over here, it really is, it looks
like a piece of RNA. It looks like you're taking a... You have ribose, you have the adenine, you have a phosphate group, and it can actually be used
to construct things like RNA and even DNA beyond just being the
molecular currency of energy. So it's fun to see how these
pieces all fit together, how they can be broken up, and you see these patterns
over and over again in biological systems, and
these biological systems are really just made up of breaking down and building back up
carbohydrates, lipids, fatty acids, cholesterols, other things, and proteins/amino acids. So this whole thing, you
know, look around you, look at your day, look at
the things you're consuming and you'll see this pattern
over and over and over again and it's all a little mind-blowing, because at the end of the day, the energy is coming from
the fusion reaction in stars and all of the heavy elements around you or even the not so heavy elements, all of the carbon, the oxygen, all of the really non-hydrogen elements, they've been made inside
of fusion reactions in stars that might have
existed billions and billions and billions of years ago, so hopefully that makes you
feel a little bit more connected to the universe.